Jan would be able to dance for 15 months.
Her $100 registration fee would bring her $400 to $300. Then, you divide $300 by $20, getting you a total of 15 months. The registration fee is only a one-time thing. You need to pay the $20 every month. The math for this is - ( 400-100=300), then ( 300 divided by 20 = 15).
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